http://www.physicsforums.com Molecular, Botany, Micro, Genetics, Ecology... en Fri, 24 May 2013 20:22:13 GMT vBulletin 60 http://www.physicsforums.com/images/physicsforums/misc/rss.jpg http://www.physicsforums.com http://www.physicsforums.com/showthread.php?t=692864&goto=newpost Tue, 21 May 2013 09:21:34 GMT 1.How did the nucleus evolve? 2.What are the pointers indicating the evolution of eukaryotes from the same branch as archea? 3.Obligate... 1.How did the nucleus evolve?

2.What are the pointers indicating the evolution of eukaryotes from the same branch as archea?

3.Obligate anaerobes, what is the end products? Does it include molecular oxygen? What is it in case of facultative anaerobes? Is there any organism that uses a substrate, which unlike nitrates, sulfates, carbondioxide etc.! does not contain oxygen?
*Lithotrophs oxidising HS- to S0 have a oxygen less substrate

4.Cell shape and rigidity conferred by cell wall or peptidoglycan layer when both are present?

5.Bacterial ribosomes are smaller than the eukaryotic ribosomes? So what is the function of the larger region? Why is it comparitively larger? What are the advantages conferred?

6.How did the plasmids evolve? What are the available theories? Only a few confer antibiotic and toxin resistance, what about those that dont?

7. How is the density gradient established in isopycnic centrifugation? Wont diffusion render the gradient useless in a short time?

8. What are motor proteins? How do they act (apart from actin and myosin)? Which book is good for information about these?

9. If the interactions between the organelles and the cytoskeleton are noncovalent, how is it regulated? Only way I can think of is change in pH(which inturn can influence things like hydrogen bonding, extent of vanderwaals forces, dipole dipole interaction, electrostatic interactions etc., )! What are the other ways, apart from pH regulation if at all, the cell uses to regulate this?

10. How is the varied cytosolic composition within a cell regulated? I mean it is the fundamental level where the controlling factor cannot be a large molecule because its presence in itself will have an influence on the composition, so is it like the rate of production and degradation of various substances in various parts of the cell are varied and since it is a dynamic and continuos process, there is no time for establishment of equillibrium of substance concentration?

11. It ia common notion that All cells have nucleus for some part of their life. Are there no structurss that appear similar to cells but have never had a nucleus? I mean like cytokinesis without nucleokinesis(similar to vesicle budding from an organelle)? N wouldnt it be more efficient to have rbc produced like this? A master cell with nucleus producing enzymes needed and a part of the cell chipping off? (Just wondering even though am aware these things are based on evolutionary selection)


These are the doubts that struck me as I read my first chapter in biochemistry in lehninger. Hope you people can help me with these and also that you find atleast a few interesting! Thanks in advance people!!! ]]> Biology skandy http://www.physicsforums.com/showthread.php?t=692864 http://www.physicsforums.com/showthread.php?t=692794&goto=newpost Mon, 20 May 2013 22:47:01 GMT Hi, I want to run an experiment to try and experimentally determine the efficiency (as in what percent of energy is converted to light) of... Hi,

I want to run an experiment to try and experimentally determine the efficiency (as in what percent of energy is converted to light) of bioluminescent bacteria (V. Fischeri), and compare it to the efficiency of a "traditional" light source, like an LED or an incandescent.

I know how I would determine the efficiency of an electrical source (measure the temperature of the source, turn it on, measure the temperature again after a set time, and use a couple of equations to determine energy lost as heat over energy consumed), but I am stuck on how I would measure the efficiency of a bacteria culture. The same temperature idea might work to determine the waste heat, but how would I find total energy consumed (or energy emitted as light)?

Any ideas would be appreciated!

Thanks, Charles ]]> Biology BritKnight http://www.physicsforums.com/showthread.php?t=692794 http://www.physicsforums.com/showthread.php?t=692570&goto=newpost Sun, 19 May 2013 20:03:27 GMT Ok, this is a "stupid" question that I probably should really know the answer to. I am researching bacterial invasion and replication within host cells, A. polyphaga to be exact. I grow the amoeba into a monolayer, add a certain number of bacteria to each sample, and allow them to incubate for 2 hours. This is done in duplicate. At two hours, I remove both sets of samples, remove the media from both, and wash the excess bacteria off gently. One set of samples gets media for the amoeba added and incubated for 46 hours (48 hours total). The first set of samples are washed and the amoeba lysed. The bacteria are serially diluted and plated to determine CFUs. The same is also done at 48 hours with the bacteria concentrated from the supernatant and lysed cells. My question is what calculations should be done to interpret what I am seeing. I will have multiple replicates by the end so everything will be averages eventually. I know one way to present this is just avg CFUs shown to indicate the amount of invasion and hopefully an increase with replication. It was also suggested that I divide the CFUs at 2 hours by the initial CFUs to show the percent that invaded...makes sense to me. I had been told that I should calculate the replication by taking the log of the CFUs at 48 hours divided by CFUs at 2 hours. What would that show? I assume they meant the log(CFUs 48/CFUs2). Any thoughts? Any suggestions with why you would recommend a certain way? ]]> Biology mastiffcacher http://www.physicsforums.com/showthread.php?t=692570 http://www.physicsforums.com/showthread.php?t=692480&goto=newpost Sun, 19 May 2013 09:39:31 GMT Hello dear PF-members.
(I'm terribly sorry if this thread is made in the wrong place. Please, if so, change its location.)

So, I'm writing a final essay in biology class (high school) and we got to pick whatever we wanted to write about more extensively. I stuck for the chemical adjustments in the body and all that.
So I'm aware of that hormones are the central topic in this essay and I've written a lot of amino acid based hormones (peptide hormones) and steroid hormones.
Now to my question: Could I add neurotransmitters and write about the substances regarding that without "flying away" to much off topic? And could there be anything else that'd be worth adding to the essay? Thx!
:tongue::approve::redface::biggrin: ]]> Biology Gliese123 http://www.physicsforums.com/showthread.php?t=692480 http://www.physicsforums.com/showthread.php?t=692084&goto=newpost Thu, 16 May 2013 18:58:32 GMT I've searched a bit in google about the vision of the common housefly but most studies are on the drosophilia.
First, am I right thinking that they see in 2 dimensions rather than 3? Because to see in 3 dimensions would require a somehow large distance between the extremum of their "eyes" and it's actually quite small compared to the separation between human eyes.

Second, I read that their vision is actually excellent in term of speed and precision. I guess that's basically why a fly can follow without any problem another fly that is zigzaging extremely fast for us. And apparently they can see the edges of objects really accurately, they have an extremely high resolution (can see better than a 1 mm thick object even 2 meters away from it http://phys.org/news129545593.html).

However I discovered by myself that I can actually approach a fly and even touch it without it seeing me. I would like to know what in their vision is failling in the following "test", or "set up":
let's say you are at about 40 cm away from a fly resting over a table. Point toward the fly with your index finger and go toward the fly slowly. It won't see it. You can go really close to it, and if you don't mind having a dirty finger you could just press the fly against the table. Obviously the fly doesn't see your finger getting bigger and bigger. Or should I say closer and closer. I have read nothing about this... So it doesn't seem a well known fact? I've tested this on many flies since I'm around 10 years of age.
So if they have such an amazing vision, how come they can't see a finger coming slowly to them?
I should mention that if you don't go toward the fly with your finger in a straight line, the fly will see you and get away as soon as you deviate from a straight line. ]]> Biology fluidistic http://www.physicsforums.com/showthread.php?t=692084 http://www.physicsforums.com/showthread.php?t=692013&goto=newpost Thu, 16 May 2013 11:14:29 GMT People have achieved injecting desired genetic code into bacteria. This is a big thing of course but it is far from creating life purely out of... People have achieved injecting desired genetic code into bacteria. This is a big thing of course but it is far from creating life purely out of chemicals.
Assuming 'life' to be the ability to interact with the environment for benefit and to reproduce, is it possible, at least theoretically, to assemble the necessary 'life chemicals' and create a living cell?
And if it is possible, what would it speak about things like intelligence and self-awareness?
Just trying to know your opinions. ]]> Biology s0ft http://www.physicsforums.com/showthread.php?t=692013 http://www.physicsforums.com/showthread.php?t=691744&goto=newpost Tue, 14 May 2013 21:38:59 GMT So I am asked this question in biology lab we aren't provided by any information to how to solve it,but we are asked to research on the internet in order to solve it.

Predict the reactions you would expect to see for the following foods if they were tested using benedict's test, iodine (I2KI) and the Bauret test. include the colour you would expect to see whether would indicate a positive or negative reaction. If you expect the reaction to be positive, state which macromolecule you would expect to be present in the greatest abudance.


So I read about Benedict's test which tells us if there is reducing sugar that is available in that food or not which means a positive test with benedict's test would have free aldehyde or ketone groups as macromolecule and colour changes for negative test would be blue and red for positive.

For Biuret test its pretty easy it would be positive for any food that contains proteins,so I know this about Biuret test.

I want to know though how can I know if a result is positive or not for benedict's test do I have to know the components of the food itself ? ]]> Biology Genericcoder http://www.physicsforums.com/showthread.php?t=691744 http://www.physicsforums.com/showthread.php?t=691571&goto=newpost Mon, 13 May 2013 22:06:54 GMT In the first chapter of "The Selfish Gene", when talking about replicating molecules, Richard Dawkins writes:

"Can we reconcile the idea that copying errors are an essential prerequisite for evolution to occur, with the statement that natural selection favours high copying-fidelity? The answer is that although evolution may seem, in some vague sense, a 'good thing', especially since we are the product of it, nothing actually 'wants' to evolve.”

I think this is a very interesting question, but I don't get the answer. If high copying-fidelity is a characteristic that is selected, wouldn't molecules, with time, present less and less variability, putting an end to evolution? ]]> Biology Master Wayne http://www.physicsforums.com/showthread.php?t=691571 http://www.physicsforums.com/showthread.php?t=691271&goto=newpost Sun, 12 May 2013 09:00:34 GMT Why can't low frequency or high frequency light enter my eye just like ordinary light? I imagine an ordinary camera should be able to detect light if it enters the lens, no matter the frequency. Am I under a misapprehension about cameras? Why can't the eye do the same?

I know this is a physics forum, but could the explanation be that we evolved to see visible light because it is more useful than lower/higher frequencies? Perhaps the answer is in biology. But whatever, I'm sure you guys will set me straight. ]]> Biology acesuv http://www.physicsforums.com/showthread.php?t=691271 http://www.physicsforums.com/showthread.php?t=691036&goto=newpost Fri, 10 May 2013 21:38:09 GMT Technological advances in the last several years (such as Japan's "dream machine") have given us crude glimpses into the visual component of the thought process. Is it possible to do the same with the auditory component of thoughts? Is there any scientific evidence suggesting that thought sounds have a detectable frequency? This is not an attempt at philosophy--I want to know if there's a physical or quantum mechanical basis for these sounds, because I refuse to believe that it's some magical process that can't be explained. ]]> Biology Cody Richeson http://www.physicsforums.com/showthread.php?t=691036 http://www.physicsforums.com/showthread.php?t=690976&goto=newpost Fri, 10 May 2013 16:33:19 GMT E.g. you cut yourself in the finger. The cells seems to know they will become part of your finger. (No lung tissue will be formed in your finger) E.g. you cut yourself in the finger. The cells seems to know they will become part of your finger.
(No lung tissue will be formed in your finger) ]]> Biology Alain De Vos http://www.physicsforums.com/showthread.php?t=690976 http://www.physicsforums.com/showthread.php?t=690476&goto=newpost Wed, 08 May 2013 06:33:51 GMT Hi, so I have a little background in biology. I took AP bio in HS and got a 5 and really enjoyed it along the way. I got a microscope for my own... Hi, so I have a little background in biology. I took AP bio in HS and got a 5 and really enjoyed it along the way.

I got a microscope for my own amusement and also to maybe spark an interest in my little brother.

What I'm having trouble with is finding good densities of moving microorganisms. I though motile microorganisms would be the best place to start, because I've always found them to be the most mind blowing part of simple bio.

I'm interesting in growing cultures in water to get some interesting stuff to look at, but first I want to inquire on the danger of doing so. I don't want to grow some deadly bacteria in my house.

Also, if it is safe, what should I put in the water to aid in growth? Will normal cooking sugar work? Should it be in sunlight? And how long for optimal results? (Conceivably, after a certain period when density would peak, I'm guessing things will start dying.) ]]> Biology TylerH http://www.physicsforums.com/showthread.php?t=690476 http://www.physicsforums.com/showthread.php?t=690185&goto=newpost Mon, 06 May 2013 20:10:13 GMT Hello,

I'm in need of someone to show me how to fit a bacterial growth curve to data in Prism, preferably using the Gompertz function. I also need someone to show me how to assess the goodness of this fit. I have many different growth curves and I need to compare the parameters. Hopefully, there are some life scientists who are familiar with math and can help me. ]]> Biology newlabguy http://www.physicsforums.com/showthread.php?t=690185 http://www.physicsforums.com/showthread.php?t=689827&goto=newpost Sun, 05 May 2013 06:01:55 GMT Why the tongue though small has such extensive lymphatic drainage? Is it just developmental relation? Or is it that tongue has high exposure to... Why the tongue though small has such extensive lymphatic drainage?
Is it just developmental relation? Or is it that tongue has high exposure to immunogenic substances(which I feel is not the case)??? ]]> Biology skandy http://www.physicsforums.com/showthread.php?t=689827 http://www.physicsforums.com/showthread.php?t=689709&goto=newpost Sat, 04 May 2013 15:31:28 GMT Which type of GABA receptors are present on dendritic spines? Also where are they present on the dendritic spine (i.e. head, neck or shaft)? Also,... Which type of GABA receptors are present on dendritic spines? Also where are they present on the dendritic spine (i.e. head, neck or shaft)? Also, how do these GABA receptors contribute to dendritic spine plasticity?

Any references would be greatly appreciated. ]]> Biology hivesaeed4 http://www.physicsforums.com/showthread.php?t=689709